Question

Reading of given Ammeter is 5 A when switch S is open. When S is closed, reading of Ammeter will be, where $r<<10\Omega$,

• A. 6.5 A
• B. 3.33 A
• C. 8 A
• D. 2.5 A

Answer 1

The correct option is B 3.33 A


Since $r<<R_{G}i<<I$
So, $I-i=I$
$V_{AB}=10i=rI---\left(1\right)$

when S is closed is $V_{AB}=10i^{\prime }=\frac{2}{3}rI---\left(2\right)$

By $\left(1\right)÷\left(2\right)$ is $\frac{i}{i^{\prime }}=\frac{1}{\frac{2}{3}}$ is $\frac{i}{i^{\prime }}=\frac{3}{2}$

$i^{\prime }=\frac{2}{3}\times 5=10/3$